Shapiro steps in driven atomic Josephson junctions

TL;DR

This paper investigates how periodically driving the barrier in atomic Josephson junctions induces Shapiro steps, revealing complex vortex and phonon dynamics and extending understanding of driven quantum systems.

Contribution

It demonstrates the emergence of Shapiro steps in atomic Josephson junctions under periodic driving, highlighting vortex suppression as a key mechanism.

Findings

Observation of step-like particle imbalance analogous to Shapiro steps

Identification of vortex suppression as a mechanism for step formation

Validation of results with classical-field and circuit dynamics simulations

Abstract

We study driven atomic Josephson junctions realized by coupling two two-dimensional atomic clouds with a tunneling barrier. By moving the barrier at a constant velocity, dc and ac Josephson regimes are characterized by a zero and nonzero atomic density difference across the junction, respectively. Here, we monitor the dynamics resulting in the system when, in addition to the above constant velocity protocol, the position of the barrier is periodically driven. We demonstrate that the time-averaged particle imbalance features a step-like behavior that is the analog of Shapiro steps observed in driven superconducting Josephson junctions. The underlying dynamics reveals an intriguing interplay of the vortex and phonon excitations, where Shapiro steps are induced via suppression of vortex growth. We study the system with a classical-field dynamics method, and benchmark our findings with a driven circuit dynamics.